1. Field of the Invention
This invention relates to microwave devices generally, and more particularly electromechanical multiposition coaxial switches with spaced radial channels.
2. Description of the Prior Art
In the aforementioned invention patented by this inventor, a multiposition microwave switch is taught which provides up to ten radially distributed positions at 11.5 gigahertz (ghz), with higher frequencies attainable for a lesser number of positions. While that invention was a significant advancement over the prior art, further advancement is required in order to increase the operational frequency range for microwave switches with ten or more positions.
A major problem exists, however, regarding the electrical performance of radially distributed multiposition microwave coaxial switches. As the number of positions increases, the desirable operational frequency bandwidth decreases.
This operational limitation is a mechanically created phenomenon. For any given electromagnetic transmission system geometry there exists certain definable boundary conditions which must be satisfied in order to sustain energy propagation over a designated frequency range in the generally desired transverse electromagnetic (T.E.M.) mode. For coaxial systems the primary conductor is a rectangular bar of some cross-sectional dimension (such as the reeds 68 of the aforesaid patent). Generally it will be placed in a rectangular cavity (such as the radial portions 34 of said patent, the cross-sectional dimensions of which are a function of those of the primary conductor. Similarly, a cylindrical primary conductor (inner conductor 56' of said patent) will define the dimensions of the cylindrical cavity (central portion 32 of said patent). Violation of these boundary conditions will produce a transmission system that can create and possibly sustain undesirable modes of transmission within the designated frequency range.
The aforesaid boundary problem, manifested in a multiple position switch, can best be understood by studying the cavity 30 of said patent. This cavity, which geometrically defines the transmission system, comprises an abrupt geometrical discontinuity from a cylindrical configuration at the center to radially emanating rectangular portions extending therefrom and terminating at peripheral conductive terminals or positions.
As the number of positions increases, the effect of the discontinuity becomes more pronounced because the diameter of the cylindrical center portion of the cavity becomes greater to accommodate the greater number of rectangular radial portions. When this diameter becomes large enough, undesirable T.E.M. transmission modes are established interfering with the desired transmission.
The obvious solution is to make the rectangular radial portions as narrow and as small as possible. But there are size limitations brought about by manufacturing tolerances, and more importantly, proper maintenance of sufficient mechanical integrity. For example, the reeds 68 of the aforesaid patent have minimal thickness which, in turn, determine how narrow the radial portions 34 can be.
The present invention improves significantly upon the aforesaid invention. This improvement is accomplished by a novel arrangement of features and parts, and extends the state of the art significantly as further discussed below.